Need to backup my whole phone before I flash a custom ROM, wondering if it can help.
I took a backup using Titanium Root Free version, user apps+system data, not sure where it got stored.
I have 1GB SD inserted on the phone right now, it didn't ask where to store the backup though.
Firstly, you don't really always need to wipe your whole phone if you are flashing a custom ROM. You need to wipe it completely only if you are switching ROMs, like Stock to CM or CM to AOKP or AOKP to CM, etc. If you are just updating, no need to wipe the whole phone unless specifically asked to.
And regarding TiBu, the backups are in the directory named TitaniumBackup. If you cannot find it, just check the number of backups by opening TiBu, and if it shows your backups then you are good to go.
Alternatively you can also try My Backup Root but I personally always prefer TiBu.